275 research outputs found
Laboratory-scale simulation and real-time tracking of a microbial contamination event and subsequent shock-chlorination in drinking water
Rapid contamination of drinking water in distribution and storage systems can occur due to pressure drop, backflow, cross-connections, accidents, and bio-terrorism. Small volumes of a concentrated contaminant (e.g., wastewater) can contaminate large volumes of water in a very short time with potentially severe negative health impacts. The technical limitations of conventional, cultivation-based microbial detection methods neither allow for timely detection of such contaminations, nor for the real-time monitoring of subsequent emergency remediation measures (e.g., shock-chlorination). Here we applied a newly developed continuous, ultra high-frequency flow cytometry approach to track a rapid pollution event and subsequent disinfection of drinking water in an 80-min laboratory scale simulation. We quantified total (TCC) and intact (ICC) cell concentrations as well as flow cytometric fingerprints in parallel in real-time with two different staining methods. The ingress of wastewater was detectable almost immediately (i.e., after 0.6% volume change), significantly changing TCC, ICC, and the flow cytometric fingerprint. Shock chlorination was rapid and detected in real time, causing membrane damage in the vast majority of bacteria (i.e., drop of ICC from more than 380 cells mu l(-1) to less than 30 cells mu l(-1) within 4 min). Both of these effects as well as the final wash-in of fresh tap water followed calculated predictions well. Detailed and highly quantitative tracking of microbial dynamics at very short time scales and for different characteristics (e.g., concentration, membrane integrity) is feasible. This opens up multiple possibilities for targeted investigation of a myriad of bacterial short-term dynamics (e.g., disinfection, growth, detachment, operational changes) both in laboratory-scale research and full-scale system investigations in practice
Forward--Backward Asymmetry in B -> X_s l^+ l^- at the NNLL Level
We report the results of a new calculation of soft-gluon corrections in B ->
X_s l^+ l^- decays. In particular, we present the first calculation of
bremsstrahlung and corresponding virtual terms to the lepton forward-backward
asymmetry, which allows us to systematically include all contributions to this
observable beyond the lowest non-trivial order. The new terms are important,
for instance the position of the zero of the asymmetry receives corrections of
O(10%). Using a different method, we also provide an independent check of
recently published results on bremsstrahlung and infrared virtual corrections
to the dilepton-invariant mass distribution.Comment: 20 pages, 5 figures. v2: typo in (4.26) corrected; discussion on
mu-dependence modifie
On the possibility of a very light A^0 at low \tan\beta
The searches at LEP II for the processes e^+e^-\to h^0Z and e^+e^-\to h^0A^0
in the Minimal Supersymmetric Standard Model (MSSM) fail to exclude regions of
the m_h,m_A plane where \tan\beta <1, thus allowing a very light A^0 (m_A< 20
GeV). Such a parameter choice would predict a light H^\pm with m_{H^\pm}< m_W.
Although the potentially large branching ratio for H^\pm \to A^0 W^* would
ensure that H^\pm also escaped detection in direct searches at LEP II and the
Tevatron Run I, we show that this elusive parameter space is overwhelmingly
disfavoured by electroweak precision measurements.Comment: 11 pages, 2 figures, Revtex, references added, minor additions to
tex
Supersymmetric contributions to B -> D K and the determination of angle \gamma
We analyze supersymmetric contributions to B^- -> D^0 K^- and B^- ->\bar{D}^0
K^- processes. We investigate the possibility that supersymmetric CP violating
phases can affect our determination for the angle \gamma in the unitary
triangle of Cabibbo-Kobayashi-Maskaw mixing matrix. We calculate the gluino and
chargino contributions to b--> u(\bar{c}s) and b-->c(\bar{u}s) transitions in a
model independent way by using the mass insertion approximation method. We also
revise the D^0 - \bar{D}^0 mixing constraints on the mass insertions between
the first and second generations of the up sector. We emphasize that in case of
negligible D^0 -\bar{D}^0 mixing, one should consider simultaneous
contributions from more than one mass insertion in order to be able to obtain
the CP asymmetries of these processes within their 1\sigma experimental range.
However, with a large D^0-\bar{D}^0 mixing, one finds a significant deviation
between the two asymmetries and it becomes natural to have them of order the
central values of their experimental measurements.Comment: 20 page
NNLL QCD Corrections to the Decay
We briefly discuss the status of the NNLL QCD calculations in the inclusive
rare B decay . Two important ingredients, the two-loop
matrix elements of the four quark operator and the bremsstrahlung
contributions, were quite recently finalised. The new contributions
significantly improve the sensitivity of the inclusive decay decay in testing extensions of the standard model in the sector of flavour
dynamics; for instance the two-loop calculation cuts the low- scale uncertainty
in half and the bremsstrahlung calculation leads to a 10% shift of the position
of the zero of the forward- backward asymmetry.Comment: 7 pages, latex, 5 figures, references adde
Alternative Approach to Branching Ratio Calculation
Since the calculation of in the framework of
QCD improved factorization method, developed by Beneke et al., leads to
numerical values much below the experimental data, we include two different
contributions, in an alternative way. First, we find out that the spectator
hard-scattering mechanism increases the value with almost 50%, but the
predictions depend on the combined singularities in the amplitude convolution.
Secondly, by adding SUSY contributions to the Wilson coefficients, we come to a
depending on three parameters, whose values are constrained by the
experimental data.Comment: 17 pages, 2 Postscript figure
B decays and Supersymmetry
I discuss how supersymmetry affects various observables in B decays, and
point out the interesting channels in the context of B factories.Comment: LaTex file of working group talk presented at WHEPP-7, HRI,
Allahabad, Jan. 200
Calculation of two-loop virtual corrections to b --> s l+ l- in the standard model
We present in detail the calculation of the virtual O(alpha_s) corrections to
the inclusive semi-leptonic rare decay b --> s l+ l-. We also include those
O(alpha_s) bremsstrahlung contributions which cancel the infrared and mass
singularities showing up in the virtual corrections. In order to avoid large
resonant contributions, we restrict the invariant mass squared s of the lepton
pair to the range 0.05 < s/mb^2 < 0.25. The analytic results are represented as
expansions in the small parameters s/mb^2, z = mc^2/mb^2 and s/(4 mc^2). The
new contributions drastically reduce the renormalization scale dependence of
the decay spectrum. For the corresponding branching ratio (restricted to the
above s-range) the renormalization scale uncertainty gets reduced from +/-13%
to +/-6.5%.Comment: 41 pages including 9 postscript figures; in version 2 some typos and
inconsistent notation correcte
NNLL QCD Contribution of the Electromagnetic Dipole Operator to Gamma(anti-B -> X(s) gamma)
We present an independent calculation of that part of the O(\alpha_s^2)
contribution to the decay width \Gamma(\bar B -> X_s \gamma) which arises from
the self-interference term of the electromagnetic dipole operator O_7. Using a
different method, we find complete agreement with a previous calculation. This
NNLL contribution is an important ingredient for the complete NNLL prediction
of \Gamma(\bar B -> X_s \gamma) which will resolve the charm quark mass
ambiguity appearing at NLL accuracy.Comment: 15 pages, uses axodraw.st
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